You probably won't like this answer...but (according to Apple) you're not supposed to search through your photos using the Finder's folder structure, you're supposed to use iPhoto for that. And to some degree, it's true, if you just let iPhoto do its thing and forget about the cryptic Finder file structure underneath it actually is easier and more convenient than rifling through all those folders. Not to mention you can screw up your iPhoto Library by digging around in the Finder manually.
I recall going through this with iTunes...for years I had all my MP3s organized in Finder folders the way I wanted them, and resisted letting iTunes organize my library. Then finally I realized all the features and tools I needed to maintain a music library were built into iTunes, and the Finder was really weak in that regard.
It is different somehow with photos, where you may often want to do things with them other than what iPhoto has to offer...but you can rename, sort, search, edit (within iPhoto or with another program), rotate, email, upload, slideshow, export, and much more from within iPhoto...what else do you need to do with photo files that requires manipulating them in the Finder? You can even drag directly from the iPhoto window into virtually any other window or application, just like it was a Finder window.
Having said all that, the new iPhoto Library is really just a special kind of folder, a package. If you right (control) click it and select "Open Package" you will see all your folders, Originals, Modified, etc. But don't mess them up!!
